Manufacture of soap



May 16, 1944. A, SCO 2,348,855

MANUFACTURE OF SOAP Original Fild May 6. 1940 0] SPENT l {g LYE C T i 7 E NEUTRAL 5ALT T FAT I [XE soumou F U 2 c cgougo 1 CK T MXXER. I HEATER T i H i4 l 5 SOAP L COOLING FLUID RCA To CONDENSER "LO v \IDACUUM UMP SPENT NEUTRAL [Z51 T E LYE r29 7% 5 RE T E. F (EVE g 14 B MIXER. COOLER PM 27 HEATER PICTZ INVENTOR *Pr shton T Scott.

ATTORNEY Patented May 16, 1944 UNITED STATES PATENT OFFICE MANUFACTURE OF SOAP Ashton 'r. Scott, Ardmore. 1a., assignmto The Sharpie: Corporation, Philadelphia, Pa... a corporation of Delaware Original application May 6, 1940, Serial No.

333,547. Divided and this application Novemher 4, 1941, Serial No. 417,747

6 Claims. (on. 260-413 co-pending application Serial No. 334,297, filed May 10, 1940, for Manufacture .of soap.

The violent agitation of the soap-containing mass is preferably continued during the progress of this material practically up to the instant when thismaterial enters the centrifugal separator I6. By continuing the agitation in this manner. the mass is maintained in a substantially homogeneous condition, with the result present application pertains to the special pro- 10 that continuous and fairly uniform feed to the cedure described on, page 12 of my prior applicentrifugal separator it becomes feasible cation by which the mixture under treatment in he centrifugal separator i may be f y that application is subjected to artificial extrac- Well wn y p d to e f ct continuous tlon of heat during passage to the centrifugal I pa ati n of aq s p as fr m t ap, and separator, 15 continuous discharge of these separated phases,

A feature of the present invention consists in as illustrated- ThiS c ntrif gal is preferably 1 the fact that it, provides procedure b which erated under atmospheric or super-atmospheric the continuous saponification reaction may be PreSSure- If a liq id al nce yp ce rif al more quickly accomplished and more fully con- P v e With' nventi nal W irs an p r troll d tha can th embcdiments of my prjor receiv ng covers is employed, it will be desirable application in which the features of the present to lnlect hot llquid into the pivi invention are omitted The manner in which cover of the centrifugal in order to assist in conthese results are attained will be more evident tinuous removal of Soap from the t i a a from consideration of the following detailed detaught in y F app c tionscription of the invention, and the attached In the above discussion, I hav r tricted mydrawing, in which,

Figure 1 represents a flow sheet'oi one preferred method of practicing the invention, and Figure 2 represents an alternative embodi merit of the invention.

3 In the practice of the invention in accordance with. Figure l of the drawing, a saponifiable mass, such as neutral fat from. container it is passed by pump it to a mixer it, where it is ed with a saponifying reagent passed from container 62 by pump it into confluence with g the source of fat in this mixer. *1 It i 1 r er iii may be any suitable type of mixer adapted to efiect violent mixing of the saponifying reagent with the source of fat, but a so multi-st'age high speed mechanical mixer is preferred for performance of the mixing function.

The g of the saponifying reagent with the fat at a saponiiying temperature results in formation of soap, and the soap-containing mass is is mixed with a salting out agent, such as a salt solution from container it, in order to condition the soap for subsequent centrifugal separation from aqueous phase. While the salt solution is indicated on the flow sheet as being added Self to consideration of features of the invention which are common to this invention and copending application Serial No. 333,54=7. While the manufacture of soap may be accomplished continuously in a satisfactory manner by the practice of these features, the process as described above has certain definite limitations as so practiced, unless the features of the present invention are also employed. Thus, in order to make most effective use of the apparatus in a process of this character, it is desirable that the saponification reaction be accomplished very promptly. But rapid saponification requires that the material to be saponified be heated to a temperature fairly close to or above the boiling point of the aqueous phase, either prior to the start of the saponification reaction, or at an early stage of that reaction. The heat of saponification is quite considerable, particularly in saponification of neutral fat with lye, as illustrated on the fiowsheet, and as practiced in the first or so-called killing" stage of the soap making procedure. As a consequence of this fact, if the fat is heated to a temperature very close to the boiling point of the aqueous phase before the beginning of the saponification reaction, the mixture will attain a temperature substantially above that boiling point by the time it reaches the centrifugal it, with the result that the procin my ess of centrifugation cannot be efficiently accomplished except by the provision of special, and relatively expensive apparatus for maintaining the centrifugal rotor and surrounding space under super-atmospheric pressure. Regardless of the pressure under which the centrifugal operates, efilcient centrifugation cannot be accomplished if the temperature of the mixture intro duced into the centrifugal is above the boiling point of the aqueous phase at that pressure. This difficulty is overcome, in the practice of the invention, by heating the saponifiable fat to a temperature sufficiently high to effect very rapid saponification by contact with the saponifying reagent, and extracting heat artificially from the resulting mixture during the course of the saponification reaction or during the passage of the saponified mass to the centrifugal, in order that efiicient centrifugation may be economically accomplished, and a higher temperature used in the saponiflcation reaction than would otherwise be consistent with efllcient centrifugation in the particular centrifugal employed.

Referring again to the drawing, the source of fat may be heated by passage through a continuous heater II, or by preheating in the container l0, and this fat may be mixed with lye in the mixer H at a temperature which causes the saponification reaction to proceed rapidly from the very outset. As heat is developed by the saponification reaction, the mixture is maintained at, or restored to, a temperature suitable for centrifugation by artificial extraction of heat from the material in the mixer.. This may be accomplished, for example, as illustrated, by providing a jacket l5 surrounding the more advanced stages of the mixer l4, and by circulating a cooling fluid through this jacket. Alternatively, it may be accomplished by providing cooling coils in the main body of the mixer, by adding a refrigerant to the material under treatment, by cooling the salt solution added to the mixture from the container 18, or by the method described hereinafter in connection with Figure 2 of the drawing. In any case, in the practice of the invention, sumcient heat is extracted artifl-- cially from the material under treatment to maintain the feed to the centrifugal at a temperature suitable for efficient centrifugation.

Persons skilled in the art will be aware of various other possible modifications of the invention. Thus, the saponifying reagent as well as the fat may be pre-heated before passage to the mixer, and the invention may also be practiced by heating the mixed stream of saponifying reagent and fat instead of heating these materials separately.

It will be seen that, by the practice of the in ventlon, the saponification reaction may be greatly speeded up, since it is possible to heat the fat to be saponified to a temperature in the neighborhood of the boiling point of water, or even in excess of that point, and thereafter cool the saponified mass to a temperature at which it may be efilciently subjected to centrifugal separation. Since the mixer I4 is preferably a closed mixer, loss by evaporation will not occur at this stage of the process, regardless of the temperature, and it is only necessary to provide sufficient artificial cooling during the later stages of saponification, or subsequent to saponification, to deliver the saponified mass to the centrifugal separator l8 at the desired temperature.

An alternative method of practicing the invention is illustrated in Figure 2 of the drawing.

In accordance with this embodiment, the fat to be saponified is passed from container 20 through heater 2| by pump 22 into mixer 25, this fat being mixed with the saponifying reagent from container 23 after passage of that reagent to the mixer 25 by pump 24. The features of this embodiment of the invention by which the saponified mass is formed are similar to those deevaporate water, which is condensed in condenser 29 and collected in receiver 30 from which it may be returned to cooler 26 if desired. This evaporation of water from the mixture causes it to be artificially cooled, and the cooled mass is then pumped by pump 28 to centrifugal 21, which eflects separation of spent lye from the saponified mass in a mamier similar to that of the operation of centrifugal i6.

Example A fat mixture containing 45% tallow, 35% coconut oil, and 20% palm oil was charged at .a uniform rate of 900 pounds per hour to a closed four compartment mixer provided with a coil for the circulation of cooling water in indirect heat exchange relationship with the fat in the last (in the direction of fat flow) of the four mixing compartments. Simultaneously, a saponifying reagent stream of 11% NaOH and 10% NaCl concentration was introduced to the first compartment of the mixer at a rate of 1150 pounds per hour with the fat stream at 220 F. and the reagent stream at 166 F., and with no cooling water being flowed through the coil. The temperature at the mixer inlet was 183 F. and at the outlet 220 F. Current consumption by the mixer motor was 21 amperes. The reaction mixture was continuously conducted to a centrifugal of the liquid balance type and there separated into two streams of partially saponified soap and spent lye respectively. During a run of one hour under these conditions, a total of 620 pounds of spent lye of 39% NaOH concentration was discharged from the centrifugal. The unreacted NaOH in this spent lye represented 1.9% of the NaOH in the reagent charge, and the utilization of NaOH in the desired saponification was therefore 98.1% complete.

Following this test, the temperature of the reagent charge was raised from 166 F. to 196 F. in response to which the temperature at the mixer inlet rose to 204 F. and at the outlet to 237 F. At the latter temperature, steam flashed in excessive amounts from the feed Jet to the centrifugal, causing turbulence within the bowl and preventing efilcient separation. A stream of cooling water was then flowed through the cooling coil in sufficient amount to reduce the mixer outlet temperature to 220 F. at which temperature the reactionmixture could be fed to the centrifugal without flashing. The temperature at the mixer inlet was unaffected. remaining at 204 1''. Current consumption by the mixer motor was 17 amperes.

During a one hour run under these conditions a total of 614 pounds of spent lye of 43% NaOH practicable by cooling resulted in a more nearly .complete utilization of the saponifying reagent and a reduction of nearly 20% in electric power consumed in the mixing step.

Various further modifications are possible within the scope of the invention, and I do notwish to be limited except by the following claims.

I claim: 7

1. In the manufacture of soap by a continuous process comprising subjecting a mixture of a saponiflable fat .and a saponifying reagent to a saponifying temperature, suiting out the resulting soap and separating soap of the resulting mixture from aqueous saponifying reagent by centrifugation, the step-comprising artificially extracting heat from the mixture after the beginning of the saponifloation reaction during the passage of the mixture to the zone of centrlfugation.

2. In the manufacture of soap by a continuous process comprising subjecting a mixture of a saponiflable fat and a saponifying reagent to a saponifying temperature, salting out the resulting soap and separating soap of the resulting mixture from aqueous saponifying reagent by centrlfugation, the step comprising artificially extracting heat from the mixture by indirect heat exchange after the beginning of the saponiflcation reaction during the passage of the mixture to the zone of centrlfugation. 4

3. In the manufacture of soap by a continuous process comprising subjecting a mixture of a saponiflable fat and a saponifying reagent to a saponifyin temperature, salting out the resultin soap and separating soap of the resulting mixture from aqueous saponifying reagent by cen uga- 4. In the manufacture of soap by a continuous process comprising subjecting a mixture of a saponiilable fat and a sapcnifying reagent to a saponifying temperature, salting out the resulting soap and separating soap of the resulting mixture from aqueous saponifying reagent by centrifugation, the step comprising artiflcally extracting heat from the mixture by passing said mixture to a zone of lower pressure than that at which initial saponiflcation is eifected, whereby to remove aqueous phase and thereby cool the mixture resulting from the saponiflcation reaction after the beginning of the saponification reaction during passage of the mixture to the zone of centrifugation.

5. In the manufacture. of soap by a continuous process comprising subjecting a mixture of tion, the steps comprising continuously heating the fat prior to confluence thereof with the saponiiying reagent and thereafter artificially extracting heat from the mixture resulting from addition of the saponi'fying reagent to the fat' after the beginning of the saponiflcation'reaction during the passage of the mixture to the zone of centrifugation.

9. saponifiable fat and a saponifying reagent to a saponiiying temperature, salting out the resulting soap and separating soap of the resulting mixture from aqueous saponifying reagent by centriiugation, the steps comprising effecting initial saponification of the fat by passing the mixture of fat and saponifying reagent through mixing apparatus 'under super-atmospheric pressure and at a temperature capable of causing saponiflcation 01' said fat, thereafter artiflcally extracting heat from the saponifled mixture by passing said mixture to a zone of lower pressure than that prevailing in the initial saponification step and removing aqueous phase from said mixture at said zone of lower pressure, and passing the mixture cooled by evaporation of aqueous phase to the zone of centrlfugation.

6. In the manufacture of soap by a continuous process comprising subjecting a mixture of a saponiflable fat and a saponifying reagent to a saponifying temperature, salting out the resulting soap and separating soap of the resulting mixture from aqueous saponifying reagent by centrliugation, the. steps comprising passing said fat and saponifying reagent at a saponifying temperature through-a mixer maintained under 7 super-atmospheric pressure under temperature and reaction conditions by which a temperature in excess of the boiling point of aqueous phase at atmospheric pressure is obtained in said mixer, thereafter cooling the saponifled mass by artiflcial extraction of heat to a temperature below the boiling point of the aqueous phase at the zone of centriiugation, and passing the cooled mixture to the zone of centrifugation -at said reduced temperature. Y

' ASHTON T. SCOTI. 

